Mechanical ventilators in the hot zone: effects of a CBRN filter on patient protection and battery life.

OBJECTIVE

In a contaminated environment, respiratory protection for ventilator dependent patients can be achieved by attaching a chemical, biological, radiological, or nuclear (CBRN) filter to the air intake port of a portable ventilator. We evaluated the effect of the filter on battery performance of four portable ventilators in a laboratory setting.

METHODS

Each ventilator was attached to a test lung. Ventilator settings were: assist control (AC) mode, respiratory rate 35 bpm, tidal volume 450 ml, positive end-expiratory pressure (PEEP) 10 cm H(2)O, inspiratory time 0.8 s, and FIO(2) 0.21. Ventilators were operated until the battery was fully discharged. We also evaluated the ventilators' ability to deliver all the gas through the CBRN filter and analyzed the pressures required to breathe through the anti-asphyxiation valve of a failed device.

RESULTS

The range of battery life varied widely across different ventilator models (99.8-562.6 min). There was no significant difference in battery life (p<0.01) when operating with or without the CBRN filter attached. Only the Impact 731 routed all inspired gases through the CBRN filter. The pressure required to breathe though the failed device was -4 cm H(2)O to -9 cm H(2)O.

CONCLUSIONS

Duration of operation from the internal battery was not altered by attachment of the CBRN filter. The use of a CBRN filter is necessary for protection of ventilator dependent patients when environmental contamination is present, although conditions exist where all gas does not pass through the filter with some ventilators under normal operating conditions.